Microtome



2, 1969 L. c. JOHNSON 3,460,417

MICROTOME Filed July 17, 1967 3 Sheets-Sheet 1 FIGURE I.

lNVNTOR LEIG HTON c. JOHNSON ATTORNEY A. 12, 3969 u... c. JOHNSON 3,4

MICROTOME Filed July 17, 1967 3 Sheets-Sheet 2 FIGURE 2.

FIGURE 3.

INVENTOR LEIGHTON C. JOHNSON ATTORNEY 1969 1.. cqJoHmsom 3,460,417

MICROTOME Filed July 17, 1967 3 Sheets-Sheet 5 FIGURE 5.

FIGURE 4.

INVENTOR LEIGHTON C. JOHNSON ATTORNEY 3,460,417 MICROTOME Leighton Clifford Johnson, Westmont, Ill., assignor to Miles Laboratories, Inc., Elkhart, Ind., a corporation of Indiana Filed July 17, 1967, Ser. No. 654,675 Int. Cl. 326d 7/06 U.S. Cl. 83-411 13 Claims ABSTRACT OF THE DISCLOSURE A microtome apparatus is described wherein a relatively stationary cutting blade cuts portions from a rotating specimen. Spacial rigidity between the specimen and the blade and accuracy of cutting thickness are obtained by holding a cam element between the shaft of the rotating specimen holder and a bearing point held by the cutting blade holder. Adjustment of the position of the cam element controls the distance between the shaft and the bearing point and thus the distance between the specimen and the cutting blade.

Background and prior art A microtome is a well-known device for cutting biological specimens into thin slices for subsequent microscopic examination. These biological specimens are generally sliced while they are quite solid. The solid bio logical specimens can be sliced at room temperature while impregnated with a parafiin or other embedding compound matrix or they can be sliced at low temperatures while frozen.

Since the resulting slices of the biological specimen must have thicknesses in the order of only several microns for proper microscopic examination, it is wellknown in the art that accuracy and control of slice thickness is highly desirable. When the microtome blade comes in contact with the specimen, the impact can cause mechanical distortion in the cutting edge of the microtome blade and result in slices which are not uniform in thickness. The impact can also cause undesirable relative movement between the blade and the specimen holder, thereby producing undesirable variation in slice thickness and slicing quality. In order to minimize this impact distortion of the blade and undesirable relative movement between the blade and the specimen holder, the prior art has employed massive microtome blades and massive specimen holders. This has tended to result in microtome apparatus which is undesirably large, heavy and expensive. Even so, the prior art microtomes still did not consistently produce uniform slices from biological specimens.

Summary of the invention This invention relates to improved microtome apparatus which is smaller and lighter in weight than prior art microtomes and which is capable of consistently producing biological specimen slices of uniform quality and controlled accurate thickness. In accordance with this invention, microtome apparatus or the like is provided comprising movable means for holding a specimen from which a section is to be cut, cooperable blade means mounted for movement toward and away from said specimen holding means, means biasing said blade means toward said specimen holding means, and adjustable spacing means comprising a cam member interposed between said specimen holding means and said blade means, said biasing means being effective to afford continuous positive contact of said blade means with said cam member and of said cam member with said specimen holding means, adjustment of the position of said cam being effective to tatcs Patent vary the position of said blade means with respect to said specimen holding means and thereby the thickness of a section to be cut from a specimen in said specimen holding means.

Description of the drawings Description of the invention Referring to FIG. 1, the improved microtome 10 has a base member 12 which is generally channel-shaped and has side walls 18 and a base 13. A member 14, which is also generally channel-shaped having side walls 20 and a base 15, is mounted within member 12 through pivot rods 16 which extend through the side walls 18 of member 12 and the side walls 28 of member 14. Member 14 is thus capable of limited pivotal movement around pivot rods 16.

Member 12 has a stepped rotatable shaft 28 which extends across the width of member 12 through the side walls 18 and below the base 15 of member 14. Shaft 28 has an intermediate specimen holder portion 30 which has a larger diameter than the remaining end portions of shaft 28. Alternatively, specimen holder 30 can be a separate sleeve keyed to shaft 28. The surfaces of shaft 28 adjacent to the intermediate specimen holder 30 form bearing surfaces 59. Specimen holder 30 has a diametrical slot 31, shown in FIG. 3, which extends perpendicular to the axis of shaft 28 and to a depth beyond said axis. Shaft 28 also has an internally threaded coaxial passage 33 which extends from one end thereof to and beyond the slot 31.

A removable arcuate specimen support 32 and speci men 34 are shown in FIG. 4. Specimen support 32 is shaped to conform to the peripheral surface of the specimen holding portion 30 of shaft 28 and also has a single support tab 36 located substantially at the mid point of the transverse dimension of support 32 and perpendicular to the axis of curvature thereof. Support tab 36 is formed with an opening 35. The specimen 34 consists of a biological material encased in a solid matrix and adheres to the peripheral surface of support 32 in a manner well-known in the art.

Specimen support 32 is placed onto specimen holder 30 so that tab 36 passes into slot 31. The center of opening 35 is located so as to normally be slightly above the axis of passage 33. A screw 29 having a conical inner end 37 and a knurled knob 86 on its outer end is threaded into passage 33 until the end 37 passes through opening 35. The conical shape of end 37 provides a camming action on the lower edge of opening 35 as screw 29 is advanced, and this pulls the specimen support 32 down into rigid close contact with the peripheral surface of the specimen holder 30. Specimen support 32 can be removed from specimen holder 30 by backing off the screws 29 until the pointed end 37 thereof is withdrawn from the slot 31.

A blade 22 having a cutting edge 23 extends across the width of member 14 through slots 24 in side walls 20. Blade 22 is rigidly held in place by thumb screws 26 which pass through walls 20 in a direction perpendicular to base 15 into contact with blade 22 and are provided with knurled heads 27. Blade 22 is thus mounted for movement toward and away from the specimen holding means, consisting of shaft 28, specimen holder 30 and removable specimen support 32 as member 14 pivotally moves around pivot rods 16.

Member 14 has two longitudinal tracks or guide means 44 positioned on the base 15 at the intersection of base 15 with side walls 20. The upper faces of tracks 44 are above the supper surface of blade 22. Tracks 44 are also not continuous in length. Starting from the right end, as viewed in FIG. 1, the tracks 44 extend to the rear edge of blade 22. The tracks 44 start again at point 46 located in front of the cutting edge 23 of blade 22 and extend to the left end of member 14. Member 14 also has a longitudinal opening 48, shown in FIG. 3 formed in the base 15 extending in width between the inner edges of tracks 44 and extending in length from edge 50 located near the left end of member 14 to edge 52 located near the right end of member 14. Specimen holder has a length, as shown in FIG. 3, which is less than the transverse dimension of opening 48. When shaft 28 rotates, it moves specimen 34 into opening 48 and into cutting relation to blade 22.

Along the bottom surface of member 14 directly beneath the tracks 44 are located means defining two bearing points. This means may be provided by bearing members 54 which may conveniently take the form of coaxial transversely extending cylindrical rods embedded about half-way in member 14. The axis of bearing members 54 is parallel to and substantially directly above the axis of shaft 28.

A generally U-shaped cam or wedge element 38 having a transverse portion 39 and two longitudinally extending arms 56 is located between the walls 18 of the member 12 with each of the arms 56 directly underneath tracks 44 and positioned between bearing members 54 and bearing surfaces 60. Each of the arms 56 has a first surface and a second surface 42, the surfaces 40 and 42 being inclined toward each other so that the vertical thickness of each arm 56 tapers in a wedge-like manner from a small value at the end 57 of each arm 56 to a larger value at the base of each arm 56 where it joins transverse portion 39. Wedge element 38 is also positioned so that the first surface 40 of each arm 56 is in contact with a corresponding bearing member 54 and the second surface 42 of each arm 56 is in contact with a corresponding bearing surface 60 of shaft 28. Rigidity of this contact is conveniently maintained by biasing means which may take the form of a helical tension spring 62 connected between a pin 64 of member 14 and an arm 66 of member 12.

Other suitable biasing means can also be employed if desired. The spacially rigid relationship between the shaft 28, wedge element 38 and blade supporting means or member 14 prevents undesirable movement between specimen 34 and blade 22 and thus eliminates the necessity for massive specimen holders and blades.

Wedge element or cam 38 is capable of adjustable rectilinear movement longitudinally of member 12. As wedge element 38 so moves, the angle of inclination between surfaces 40 and 42 of wedge arms 56 causes the distance between bearing members 54 and bearing surfaces 60 to change. This causes movement of the cutting edge 23 of blade 22 with respect to the specimen 34 mounted in specimen holder 30. This movement of wedge element 38 thus controls and determines the thickness of sections cut from specimen 34 by blade 22.

Wedge element 38 does not continuously move during rotation of the specimen, but moves in incremental steps when the specimen 34 is out of cutting relation with the blade 22, said movement representing the thickness of a subsequent individual section to be cut by blade 22 from specimen 34. Movement of wedge element 38 is accomplished in the following described manner.

As shown in FIG. 2, screw 58 is threaded longitudinally through the transverse portion 39 of wedge element 38. When screw 58 is rotated, wedge element 38 moves therealong, the longitudinal direction of said movement depending upon the direction of rotation of screw 58. A bearing block 55 is mounted on base 13 of member 12. An unthreaded extension 59 of screw 58 extends through a suitable bore in bearing block 55 and has a helical gear 80 keyed thereon. Helical gear 80 engages helical gear 78 which is keyed to a transverse shaft 74 which extends through a suitable bore in bearing block 55 and is located below the screw 58. A handwheel 84 having an eccentric handle 65, shown in FIGS. 3 and 5, is fixed coaxially to shaft 74 and thereby to helical gear 78. Gross movement of wedge element 38 can be accomplished, if desired, by turning handle to rotate handwheel 84 in either desired direction. Clockwise rotation of handwheel 84, as viewed in FIG. 5, will move wedge element 38 to the left, as viewed in FIG. 2. counterclockwise rotation of handwheel 84, as viewed in FIG. 5, will move wedge element 38 to the right, as viewed in FIG. 2.

A spur gear 68 is fixed to and rotates with shaft 28. This gear in turn engages a rotatably mounted spur gear 70 which engages spur gear 72 which is fixed to a suitably mounted rotatable transverse shaft 63. Also fixed to shaft 63 is five-toothed spur gear 61. Gear 61 engages a spur gear 73 which is rigidly connected to a pawl carrier 76. Pawl carrier 76 is located in an arcuate extension 69 of a. circular opening 67 formed in the adjacent sidewall 18 of member 12. Opening 67 is coaxial with shaft 74. Gear 73 and pawl carrier 76 are freely rotatably mounted on shaft 74 and are connected to one end of tension spring 77 which has its other end anchored to the member 12 and tends to rotate gear 73 and pawl carrier 76 in a clockwise direction (as viewed in FIG. 2) to the position shown in FIG. 2. A rotatable ratchet wheel 79 is fixed to shaft 74. Pawl 81 (shown in FIG. 5) is pivotally supported on pawl carrier 76 by means of pivot 51 which extends from pawl carrier 76 transversely through pawl 81. Pawl 81 is biased into engagement with ratchet wheel 79 by means of a tension spring 83 (shown in FIG. 2) which is anchored to pawl carrier 76 at one end and has the other end connected to transversely extending bias pin 49 on pawl 81.

As shaft 28 rotates in a clockwise direction, as shown in FIG. 2, it causes five-toothed gear 61 to also rotate in a clockwise direction through the above-mentioned gear train. The teeth on gear 61 are located so that they engage the teeth of gear 73 only after the shaft 28 has rotated to a position wherein specimen 34 has completely passed the cutting edge 23 of blade 22. Continued rotation of shaft 28 causes gear 61 to rotate gear 73, pawl carrier 76 and ratchet wheel 79 in a counterclockwise direction. Rotation of gear 61 rotates pawl carrier 76 against the action of spring 77 from the upper portion to the lower portion of arcuate extension 69 of opening 67, which is the distance of ten ratchet teeth along ratchet wheel 79. This causes rotation of shaft 74, helical gears 78 and and screw 58 which in turn causes movement of wedge element 38 toward the left as shown in FIG. 2.

As gear 61 continues its clockwise rotation so that its five teeth are moved out of engagement with the teeth of gear 73, movement of wedge 38 stops. Spring 77 then moves pawl carrier 76 and gear 73 in a clockwise direction to return pawl carrier 76 to its upper position shown in FIG. 2 without corresponding clockwise movement of ratchet Wheel 79. Pawl carrier 76 and gear 73 are now ready for another cycle of operation for incremental movement of wedge 38.

The amount of movement of wedge 38, and thus the thickness of a slice cut from specimen 34 is controlled by the total movement of ratchet wheel 79 per revolution of gear 61. An adjustment sleeve 82, shown in FIGS. 3 and 5, coaxially surrounds the handwheel 84 and has a reduced diameter portion 85 which extends inwardly to overlie the ratchet wheel 79 and is positionable between pawl 81 and ratchet wheel 79 to thereby hold pawl 81 out of engagement with said ratchet wheel. Cylindrical extension portion 85 has an arcuate segment removed therefrom to form an opening 87 which exposes a portion of the periphery of the ratchet wheel 79 and has a circumferential length equal to at least ten ratchet teeth on ratchet wheel 79. The circumferential length of the remaining portion of the extension 85 is equal to at least ten ratchet teeth on ratchet wheel 79. Adjustment sleeve 82 can be rotated so as to position any selected amount of opening 87 between pawl 81 and ratchet wheel 79 and selectively expose from zero to ten ratchet teeth. If adjustment sleeve 82 is rotated, as shown in FIG. 5, so that the opening 87 allows pawl 81 to engage ratchet wheel 79 when pawl carrier 76 is in the upper portion of arcuate opening extension 69, shown in FIGS. 2 and 5, then a single revolution of gear 61 will cause ratchet wheel 79 to move a rotational distance of ten ratchet teeth as pawl carrier 76 is being moved to the lower portion of arcuate opening extension 69. If adjustment sleeve 82 is rotated so that opening 87 is positioned, for example, to expose only two ratchet teeth, as shown in FIG. 2, then pawl 81 can only engage ratchet wheel 79 when pawl carrier 76 has been moved almost to its lower limit and thus move ratchet wheel 79 a rotational distance of only two teeth for each revolution of gear 61.

Movement of ratchet wheel 79 a rotational distance of one ratchet tooth will cause longitudinal movement of wedge 38 a sufficient amount to result in a slice thickness of two microns, for example. This apparatus can thus produce controlled slice thicknesses from two microns to twenty microns per slice in selected thickness increments of two microns. It should be noted and understood that such slice thicknesses are merely illustrative. Other thicknesses can be produced depending on the particular design of the apparatus with respect to shape and size of the wedge or cam member 38, number and size of ratchet teeth on ratchet wheel 79 and gear ratios of all the driving gears involved.

The microtome can be manually operated by turning shaft 28 in a clockwise direction shown in FIG. 2. This can be accomplished by gripping and turning the knurled knob 86 threaded into one end of shaft 28. This will rotate specimen 34 into cutting relation to the blade 22. The gear train connected to shaft 28 will also cause incremental movement of wedge element 38 to the left, as viewed in FIG. 2, causing the blade 22 to be lowered the desired section thickness after each section is cut in readiness for cutting a subsequent section. For motorized operation, a rotatable transverse shaft 88 located parallel to and below shaft 28 is suitably mounted in the member 12 and has a spur gear 90 keyed thereto which engages the spur gear 70. Rotation of shaft 88 by a suitably connected motor (not shown) will thus cause the same effects as the manual rotation of shaft 28 aforedescribed.

In preferred forms of the invention, the microtome can have additional features. In one such feature conveying means are provided for advancing a substrate, such as a microscope slide along the guide tracks 44 in timed relation with cutting of a section from the specimen 34. To this end an endless chain 92 is recessed in one side wall 20 of member 14 and is trained around suitably mounted idler sprockets 101 and 103. As shown in FIG. 2, a spur gear 93 which is freely mounted on the pivot rod 16 is connected through a gear train consisting of suitably mounted rotatable spur gears 95 and 97 to gear 72. Gear 93 also engages a rotatably mounted spur gear 75' which engages spur gear 89 which is fixed to a suitably mounted rotatable transverse shaft 71. Also fixed to shaft 71 is a drive sprocket 94 which engages both the upper and lower extents of the chain 92. Clockwise rotation of shaft 28 thus causes counterclockwise movement of chain 92, as viewed in FIG. 2. A drive finger 96 is carried by the chain 92.

The guide means or tracks 44 are adapted to have a substrate, such as a microscope slide or a continuous film, placed thereon and moved longitudinally therealong. When a slide is used, as in the illustrated form of the invention, an abutment 91 is located on base 15 near the left end of member 14 as shown in FIGS. 2 and 3. A microscope slide 98 is placed on tracks or guide means 44 in abutting relation to abutment 91, and when the microtome 10 is operated to move specimen 34 into cutting relation with blade 22, the indicated movement of chain 92 will cause drive finger 96 to move into engagement with slide 98 and thus move slide 98 along tracks 44 and across opening 48 in close proximity to the exposed peripheral surface 100 of specimen 34. as a section is being cut from the specimen, so that the cut section will be laid against the underside of the slide and readily adhere thereto. The cut section will be laid against the underside of slide 98 without any prior contact of the slide with specimen 34. The linear speed of the movement of slide 98 matches the linear speed of the section being cut so that no additional stresses are placed on the section as it is laid against the slide.

At the completion of cutting a single section, the slide with the section mounted thereon moves to the right end of the microtome, as vie-wed in FIG. 2, where it can be conveniently removed for further use. A new slide can then be placed in position on tracks 44 against the abutment 91 in preparation for the next cutting cycle. When a continuous film type of substrate is used, any suitable film feed and take-up means may be provided to feed the film along suitable guide means in proximity to the exposed peripheral surface of the specimen in timed relation with the cutting of a section from said specimen.

It is well-known in the microtome art that the first few sections cut from a specimen are generally unsatisfactory. Usually, the third slice or section is quite satisfactory. In a further preferred form of the apparatus, the gear chain ratios, the length of chain 92 and the location of drive finger 96 are selected so that a substrate, such as slide 93, is moved into proximity with specimen 34 only every third revolution of shaft 28. This apparatus modification is intended primarily for cutting and mounting on a substrate surface a single slice from a given specimen. If several slices are to be cut and mounted from a given specimen in a continuous fashion, only the first two slices need be discarded. All the subsequent slices cut at that time can be used, and the apparatus can be modified to pass a substrate surface over the specimen while cutting each of said subsequent slices.

In still a further preferred apparatus form, member 12 is suitably enclosed and a vent 102 is provided adjacent the specimen holding means and blade means at the right end of member 12 as shown only in FIG. 2 and as shown from the opposite side in FIG. 5. A vacuum line communicating with a vacuum pump (not shown) can be attached to vent 102. The applied vacuum is effective to remove unwanted sections and other debris during operation of the microtome.

In summary, this invention relates to an improved microtome wherein spacial rigidity is maintained between a specimen and a blade so that sections of uniform desired thickness can be obtained without resort to massive heavy specimen supports and blades. It also relates to an automatic microtome wherein sections can be cut and mounted on a substrate in a single operation.

What is claimed is:

1. A microtome apparatus or the like comprising movable means for holding a specimen from which a section is to be cut, cooperable blade means mounted for movement toward and away from said specimen holding means, means biasing said blade means toward said specimen holding means, and adjustable spacing means comprising a cam member interposed between said specimen holding means and said blade means, said biasing means being effective to afford continuous positive contact of said blade means with said cam member and of said cam memher with said specimen holding means, adjustment of the position of said cam being effective to vary the position of said blade means with respect to said specimen holding means and thereby the thickness of a section to be cut from a specimen in said specimen holding means.

2. Apparatus according to claim 1 having a rectilinearly movable wedge-shaped cam member.

3. Apparatus according to claim 1 having guide means defining a path along which a substrate can be moved in proximity to a specimen being cut and in a position to permit a cut section to be laid thereagainst as said section is removed from the specimen by the blade.

4. Apparatus according to claim 3 having conveying means for advancing said substrate along said guiding means in timed relation with the cutting of a section from said specimen.

5. Apparatus according to claim 1 wherein the blade means is mounted for pivotal movement.

.6. Apparatus according to claim 1 wherein the cam adjusting means is driven by movement of the specimen holding means.

'7. Apparatus according to claim 4 wherein the conveying means is driven by movement of the specimen holding means.

8. Apparatus according to claim 1 wherein vacuum type debris removal means is provided adjacent said specimen holding means and blade means.

9. Apparatus according to claim 1 employing a rotary specimen holding means.

10. Apparatus according to claim 9 wherein the rotary specimen holding means is capable of presenting a specimen held thereby to the blade means during only a por tion of its rotary movement, and there is means for adjusting the position of said cam member when the specimen holding means is disposed in another portion of its rotary movement.

11. A microtome apparatus or the like comprising movable means for holding a specimen from which a section is to be cut, cooperable blade means for cutting a section from said specimen, and guide means defining a path along which a substrate can be moved in proximity to said specimen being cut and in a position to permit a cut section to be laid thereagainst as said section is removed from the specimen by the blade.

12. Apparatus according to claim 11 having conveying means for advancing said substrate along said guiding means in timed relation with the cutting of a section from said specimen.

13. Apparatus according to claim 12 wherein the conveying means is driven by movement of the specimen holding means.

References Cited UNITED STATES PATENTS 775,556 11/1904 Dieckmann. 3,293,972 12/1966 Burkhardt et a1. 83--915.5 X

WILLIAM S. LAWSON, Primary Examiner U.S. Cl. X.R. 8340l, 433, 915 

